Lower Unit '97 25 HP Mercury

bw44

Recruit
Joined
Jan 27, 2003
Messages
3
I have 1997 25 HP Mercury (oil/gas mix motor). The engine runs great, except for a slight timing issue since I had some carb. work last summer. A few months back I took the motor off to do some transom work on my boat. When I put the motor back on and attached the water hose, the motor started right up.<br /><br />The next day, I took it out to go duck hunting and again it started right up...no problems. So I'm idling out and start to give it gas, just about the time the boat starts to plane the prop spins out as if something is stripped. At first I thought I was still in shallow water and the prop was stuck in some moss, but that certainly wasn't it.<br /><br />When in forward gear (engine off), the prop will turn in the proper direction with a slight clicking sound which I was told is normal. When trying to turn the other direction, it won't spin which I was also told is normal.<br /><br />I hadn't changed the lower unit oil in almost a year, but I thought that was OK considering my usage. I checked after the fact and it looked fine, ie. no shavings or other foreign objects.<br /><br />I'm not the greatest mechanic and am curious if this sounds fixable without the help of a pro (aside from parts, of course). I want my motor fixed, I just can't justify the $200-300 a mechanic will charge unless it is absolutely necessary.<br /><br />Thanks in advance to your respones.<br /><br />BW
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: Lower Unit '97 25 HP Mercury

bw44,Check to see if your prop hub is spun.That's what it sounds like from your description.However in gear,with motor off,the prop should not be easy to rotate if prop is not spun.
 

bw44

Recruit
Joined
Jan 27, 2003
Messages
3
Re: Lower Unit '97 25 HP Mercury

Hub? I'll be honest....I'm not sure what/where that is. I did take the prop off and everything seemed fine there. The prop's shaft had grooves on it which I assumed to be standard...no wear marks. Is the hub some sort of rubber part, or am I confusing that with something else? <br /><br />I've just been a little hesitant to delve into the lower unit area. What I really need is a manual of some sort so that I can see what it SHOULD look like. Is it possible to get a manual for this motor?
 

ob

Admiral
Joined
Aug 16, 2002
Messages
6,992
Re: Lower Unit '97 25 HP Mercury

bw44,The hub is the rubber jacketed spline in the center of propeller.It serves as a torque and impact damper.Check the edges of it to see that they have not slipped or "spun."Sometimes they will only spin under load which can be verified by scribing two marks .One on hub and one on prop barrel and see if they stay lined up after load is applied.
 

bw44

Recruit
Joined
Jan 27, 2003
Messages
3
Re: Lower Unit '97 25 HP Mercury

Thank you for your help OB. I searched the archives using "hubs" and came up with a prior post describing my exact same circumstances. <br /><br />What I failed to mention was that the last time I was out and my motor was running fine, I ran into an old trot-line and it wrapped my motor. I didn't notice any problem because we went real slow back to the boat ramp from that point.<br /><br />I can live with a $40-50 repair bill, I just hope that the hub is all that is wrong with it. Thanks, again.........GREAT FORUM!!
 
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